Another vote list. Kate O'Beirne offers a list of "Republican senators whose intentions are unknown" and who could be crucial for opponents in the cloture vote:

Richard Burr (N.C.), Lamar Alexander (Tenn.), Kit Bond (Mo.), Pat Roberts (Kan.), Gordon Smith (Ore.), Thad Cochran (Miss.), Mike Crapo (Ind.), Norm Coleman (Min.), Kay Bailey Hutchison (Tex.), Orrin Hatch (Utah), Bob Bennett (Utah), and John Sununu (N.H.).

She also says that opponents "hope they can count on about a dozen democrats." My guess who they might be likely thinking of (based on my list): Webb, Dorgan, Byrd, Tester, Baucus, Rockefeller, Pryor, Landrieu, and McCaskill. That's 9. Throw in Independent Sanders and you might have 10. Two others? Maybe Nelson? Bingaman? Someone else?